1. Field of the Invention
The present invention relates to organic compounds, anthracene derivatives, and light-emitting elements, light-emitting devices, and electronic devices each of which use the anthracene derivatives.
2. Description of the Related Art
Light-emitting elements that use light-emitting materials have advantages of being thin, being lightweight, and the like, and are expected to be applied to next-generation displays. Further, since the light-emitting elements are self-light-emitting elements, the light-emitting elements are superior to liquid crystal displays (LCDs) because they have high visibility without a problem such as a viewing angle.
A basic structure of a light-emitting element is a structure in which a light-emitting layer is included between a pair of electrodes. It is said that, when a voltage is applied to such a light-emitting element, holes injected from an anode and electrons injected from a cathode are recombined with each other in a luminescent center of the light-emitting layer to excite molecules, and the molecular excitons release energy in returning to a ground state, whereby light is emitted. It is to be noted that excited states generated by the recombination include a singlet state and a triplet state. The light emission can be obtained in either of the excited states. In particular, the light emission occurring when the singlet-excited state directly returns to the ground state is referred to as fluorescence, and the light emission occurring when the triplet-excited state returns to the ground state is referred to as phosphorescence.
With such light-emitting elements, there are a lot of material-related problems for improvement of element characteristics. In order to solve the problems, improvement of an element structure, development of materials, and the like have been carried out.
For example, in Patent Document 1: United States Patent Application Publication No. 2005-0260442, an anthracene derivative that emits green light is described. However, Patent Document 1 discloses only the emission spectrum of the anthracene derivative but not the device performance for when the anthracene derivative was applied to a light-emitting element.
Also, in Patent Document 2: Japanese Published Patent Application No. 2004-91334, a light-emitting element in which an anthracene derivative is used for a charge transporting layer is described. However, in Patent Document 2, there is no description of the life of the light-emitting element.
If commercialization is considered, extending the life of the light-emitting element is an important issue. Further, the development of light-emitting elements with much higher levels of performance is desired.